35
SECTION FIVE
APPLICATIONS
CURRENT LIMIT TRIPS
UNSTABLE
MOTOR OPERATION
Excessive loading of the VLT may result in "CURRENT LIMIT" trips.
This is not a concern if the unit has been properly sized and intermittent
load conditions cause anticipated operation in current limit. Nuisance
current limiting and unstable motor operation can, however, be caused
by improperly setting specific parameters. The following parameters
are those which are most critical to the VLT/Motor relationship.
100 - Load Type
103 - Motor Power
104 - Motor Voltage
105 - Motor Frequency
107 - Motor Current
108 - Motor Magnetizing Current
109 - Start Voltage
110 - Start Compensation
209 - Current Limit
Parameter 100
An incorrect setting may provide an improper voltage to frequency ratio
to the motor with respect to the load demand. For example, a constant
torque (CT) load requires a higher V/F ratio at start-up than a variable
torque (VT) load. If a VT mode of operation has been selected when
operating a CT load, improper starting torque will be available.
Parameters 103, 104, 105, 107
These parameters, when incorrectly set, have an effect on other
parameters as well as the unit's interpretation of the load. In setting
these parameters enter the name plate data from the motor into the
appropriate parameter. Use the conversion chart to change from HP to
KW.
HP 1 2 3 5 7 10 15 20 30 40 50 60 75
kW 0.75 1.5 2.2 4.0 5.5 7.5 11 15 22 30 37 45 55
HP 100 125 150 200 250 300
kW 75 90 110 160 185 200
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